Various synthetic polymers are typically produced from petro-chemical sources via well-known chemical processes. In recent years, the industry has renewed its focus on biopolymers from environmentally friendly, renewable sources of plants, animals and other living organisms. Extracting or separating the biopolymers from their natural sources often employs large quantities of volatile organic solvents or other undesirable chemical solvents. It is highly desirable to use a “green solvent” to extract and process biopolymers.
In recent years, ionic liquids have been extensively evaluated as environmental-friendly or “green” alternatives to conventional organic solvents. Generally speaking, ionic liquids refer to a specific class of molten salts which are liquids at temperatures of 100° C. or below. Ionic liquids have very low vapor pressure and generate virtually no hazardous vapors. Moreover, ionic liquids are composed of charged species, which provide a highly polar medium useful in various applications, such as extraction, separation, catalysis and chemical synthesis medium.
Ionic liquids have been used to dissolve or treat cellulosic materials and starch. Such applications are described in U.S. Pat. No. 1,943,176; U.S. Pat. No. 6,824,599; WO 05/29329; WO 05/17001; WO 05/17252; and WO 05/23873.
It has now been found that other biopolymers can be dissolved in ionic liquids. It has also been found that other biopolymers can be extracted or separated from their natural biological sources using ionic liquids. It is surprising to find that certain biopolymers that are insoluble or have very limited solubility in water or organic solvents can be dissolved in ionic liquids, and extracted from their biological sources with ionic liquids.